That's another issue - no spark yet but I got a deal on another primary coil and CDI box to test with. But figured I could at least get a good compression test before sorting the no spark issue.

Oh, haha. So its not over yet, she cried.

Rings fitting grooves "a lot easier" might not be okay.  Not sure what that means. 

I put the lower ring into the cylinder and held it up to the light. Looks like I can see light on one side, no surprise there I guess was impossible to remove without bending it some. Then I tried the top ring which came loose a lot easier so I am assuming it is not bent from me anyway. Looks like I can see some light on the side of that ring too but harder to tell. When I get off from work I am going to try rotating the ring in the cylinder to see if the light gaps follow the rings or not.

@markt Still not sure if incorrect ring was forced in there or not. Looks like it was just corroded and some cleanup lets it move in an out of the grove in what seems like a normal fashion. Need to try and get a feeler in the groove after I clean it up, at least to try and determine if it is the correct ring for this piston.

So the ring in the cylinder/light trick is a great way to check your rings and cylinder. I saw lots of light from bent bottom ring. Top ring shows light in only one small spot but when rotating ring a few degrees the light did not move with the ring it stayed put. So my cylinder appears to be crap too. I am going to guess that 4th oversize might be a waste of time and maybe a replacement cylinder is in my future bank account permitting.

Take some pictures of your cylinder bore and post

Nothing to lose by puting it back together & run her around the block. I'd chek the ring halfway between top & the exhaust port at exactly the possition the ring peg would hold it when looking for light as the exhaust port likely wears the ring more than the others. On my KX i knew when a ring was needed as lost the sharp edge of power & every time i could see daylight inline with exhaust port & a new ring always fixed it.

Here is a couple pics of the cylinder. Some of the crusty spots are where I can see some light with the top ring in place. I measured the piston and cylinder as best I could with my old Craftsman dial caliper and get about 85.64mm across the top of the piston (my caliper is a little shallow to read from the side) and around 85.598 - 85.674 mm inside the cylinder. According to the bottom ring it is .75 over. I can't imagine squeezing another. 0.25mm out of it for 4th over. I think the space between the ring and cylinder is already close to a 1/4 millimeter. Unless I am missing something in my calculations. I hope I am wrong. Thanks again for all the replies.
 

In the interest of 'Not spending money' i'd slide the piston in with a feeler blade to find the clearance at the skirt & see if its in with a chance. Give the cylinder a scratch first to clean up the rust. Could wrap a turn of some emery paper around something get up there for size to revolve with a drill as slow as it'll go & move up & down. Cylinder is designed to go out to 1mm over with yamaha genuine kits if you have to. But i'd be doing it the cheap way to get it running & see what else is going on. I can see a mark down around the ports or is it just where the piston & rings stopped while it was parked for a long time.

If it’s within specs as Rt325 says I would camfer the ports, hone the cylinder walls and use new rings